https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63432
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> --- r215830 introduced: /* Scale up the frequency by REG_BR_PROB_BASE, to avoid rounding errors applying the edge probability when the frequencies are very small. */ epath->src->count = epath->src->frequency * REG_BR_PROB_BASE; FOR_EACH_EDGE (esucc, ei, epath->src->succs) esucc->count = apply_probability (esucc->src->count, esucc->probability); Can it guarantee that esucc->src->count has been scaled up by REG_BR_PROB_BASE from esucc->src->frequency?